Articles you may be interested inXray reflectivity study of behenic acid Langmuir-Blodgett mono and multilayers on SiO2 surfaces asdeposited and after thermal treatment: Influence of substrate/film interactions on molecular ordering and film topology Static and dynamic structural analysis of a saturated solution of ZnBr2 in water: Anomalous xray diffraction and molecular dynamics simulations Near edge xray absorption fine structure investigation of the orientation and thermally induced order-disorder transition in thin organic films containing long chain hydrocarbons Higher order structure analysis of nanomaterials by spectral reflectance of laserplasma soft xray AIP Conf.An efficient numerical analysis procedure of x-ray reflectivity data from ultrathin organic films at interfaces is presented. It allows virtually exact modeling of reflectivity data in the entire q-vector range including the critical angle and below with minimum fit parameters and calculation effort. The electron density profile is interpreted as a linear superposition of the air/film interface, the internal film structure, and the film/substrate interface. The reflectivities at the interfaces are calculated from the accurate Fresnel reflectivities. The internal film structure is parameterized in a Fourier series and its reflectivity contribution is calculated from refraction-corrected, approximated ͑linearized͒ Fresnel reflectivities. Additionally, a new way of weighing measurement errors is introduced. It allows the selective optimization of the fit in those data sections which are considered especially significant. Finally, we show further how to determine the degree of correlation ͑interdependencies͒ between the fit parameters and how to obtain absolute errors ͑the significance͒ of all fit parameters.

Langmuir–Blodgett films of various layer numbers of behenic acid on SiO2 surfaces were investigated by x-ray reflectivity before and after thermal treatment (annealing). The thicknesses of the monolayers at the substrate/film interface indicate that the molecules are oriented normal to the interface. For samples without further treatment, at some distance from the interface, three different layer spacings are found which correspond to molecular tilt angles of 21, 28, and 36 deg. The transition region of decreasing layer spacings extends roughly over the first five layers. The films are not in equilibrium after deposition. Their molecular packing and topology can be altered irreversibly by thermal treatment (annealing) at temperatures well below the main phase transition into an isotropic phase. Whereas the molecular ordering of the first monolayer is hardly affected by the heating, all other layer spacings are uniform after the heating, with molecular tilts of 36 deg. In the case of thick multilayers the thermally induced restructuring is accompanied by an increase of the total layer number due to the reduced layer spacing and material conservation. Thin multilayers breakup into multilayer islands and monolayer-covered substrate surface (dewetting).